I'm not sure about the Group Policy, but maybe this will help?

------------

Look in the docs folder of the Server Administrator Installation Package (it gets extracted on your hard drive).  In this folder:  srvadmin\docs\en\OpenManage_IS_UG

 

Open index.htm

Select the link:  "Installing Managed System Software on Windows Operating Systems"

Select the link:  "Installation Procedures"

Browse down until you find the section titled "Performing an Unattended Installation of Managed System Software"

 

Maybe that has some useful information.  Let me know whether or not that is helpful.